The invention relates generally to a yaw damper for non-driven wheels of a two-wheel drive motor vehicle and more particularly to a yaw damper having a passive torque transfer device which is operably disposed between the non-driven wheels of a two wheel drive motor vehicle.
The benefits of front wheel drive in motor vehicles, particularly passenger cars and minivans, are generally recognized and acknowledged. Superior traction due to the weight of the engine being primarily borne by the front (driving) wheels improves traction on wet roads and in snow, ice and other low traction conditions. Front wheel drive configurations also tend to be space efficient and therefore are favored by both automobile manufacturers and users of compact and intermediate size vehicles.
Front wheel drive powertrains are not without some disadvantageous aspects, however. Front wheel drive vehicles are subject to torque steer which can be disconcerting to drivers unaccustomed to it. Front wheel drive vehicles also tend to be front heavy which can affect driving dynamics. Vehicle handling during a skid can be problematic if only because proper recovery from a skid in a front wheel drive vehicle requires counter-intuitive driver input. That is, if a front wheel drive vehicle begins to over steer or xe2x80x9ccome around,xe2x80x9d to straighten the vehicle, the driver must accelerate to pull the front out of the skid rather than let up on the throttle, a reaction which is appropriate for a rear wheel drive vehicle. Accordingly, while a front wheel drive vehicle may be more stable in low traction driving situations, once a skid or oversteer has commenced, correction may be more difficult for a typically skilled driver to achieve.
The present invention is directed to a device for improving stability and skid recovery of a front wheel drive vehicle.
A yaw damper for a two wheel drive vehicle provides torque transfer between the two non-driven wheels and generates a damping yaw moment in opposition to the current vehicle yaw moment. The yaw damper is passive and includes a mechanical clutch or pump and fluid connection between the two non-driven wheels which transfer yaw correcting torque. In one embodiment, the mechanical clutch includes first and second pluralities of interleaved friction disks which are coupled by shafts to respective non-driven wheels. A spring compresses the clutch pack and limits torque transfer between the shafts and wheels to a pre-selected maximum. The clutch may be disposed either in the center of the vehicle or adjacent one wheel. In another embodiment, positive displacement pumps driven by each of the non-driven wheels are connected in series and transmit torque in proportion to the speed difference. A pressure relief valve limits the maximum pressure in the fluid lines and thus the maximum torque transfer. In another embodiment, nested shafts include centrifugal clutches which transfer torque in proportion to the vehicle speed and the speed difference between the wheels. Mechanical stops limit maximum torque transfer between the wheels.
Thus it is an object of the present invention to provide a yaw damper coupled to the non-driven wheels of a two wheel drive vehicle.
It is a further object of the present invention to provide a yaw damper coupled to the rear wheels of a front wheel drive motor vehicle.
It is a still further object of the present invention to provide a passive yaw damper for the rear wheels of a front wheel drive vehicle which includes a friction clutch assembly.
It is a still further object of the present invention to provide a passive yaw damper for the rear wheels of a front wheel drive vehicle which includes interconnected fluid pumps driven by the rear wheels.
It is a still further object of the present invention to provide a passive yaw damper for the rear wheels of a front wheel drive vehicle which includes nested tubes having a torque limiting centrifugal clutch.
Further objects and advantages of the present invention will become apparent by reference to the following description of the preferred and alternate embodiments and appended drawings wherein like reference numbers refer to the same component, element or feature.